Effects of two sludge application on fractionation and phytotoxicity of zinc and copper in the soil

The potential harm of heavy metals is a primary concern in application of sludge to the agricultural land. A pot experiment was conducted to evaluate the effect of two sludges on fractionation of Zn and Cu in soil and their phytotoxicity to pakchoi. The loamy soil was mixed with 0%, 20%, 40%, 60% and 80% (by weight) of digested sewage sludge (SS) and composted sludge (SC). The additions of both sludges caused a significant raise in all fractions, resulting in that exchangeable (EXCH) and organic bound (OM) became predominance of Zn and organic bound Cu occupied the largest portion. There was more available amount of Zn and Cu in SS treatments than SC treatments. During the pot experiment, the concentration of Zn in EXCH, carbonate (CAR) and OM and Cu in EXCH and OM fractions decreased in all treatments, so their bioavailability reduced. Germination rate and plant biomass decreased when the addition rate was high and the best yield appeared in 20% mixtures at the harvest of pakchoi. The two sludges increased tissue contents of Zn and Cu especially in the SS treatments. Zn in pakchoi was not only in relationship to ΔEXCH and ΔCAR forms but also in ΔOM forms in the sludge-soil mixtures. Tissue content of Cu in pakchoi grown on SC-soils could not be predicted by ΔEXCH. These correlation rates between Zn and Cu accumulation in pakchoi and variation of different fractions increased with time, which might indicate that sludges represented stronger impacts on the plant in long-term land application.     

粉煤灰钝化污泥人工土壤理化性质研究

通过添加不同比例的粉煤灰对城市污泥进行钝化,对钝化污泥的pH值、养分含量及重金属含量变化以及各配比人工土壤的持水性能进行了研究,评价其用于无土排岩场生态修复的可行性.结果表明,当粉煤灰与污泥以Ⅲ(1:1)和Ⅱ(2:1)配比时,人工土壤持水性能高于对照(草甸棕壤),以Ⅳ(1:2)配比时,持水性接近于对照;粉煤灰钝化污泥中养分含量极其丰富,处于高肥力水平,随着粉煤灰添加量的增加,人工土壤的养分含量呈现降低趋势;粉煤灰钝化污泥人工土壤中除了Ⅲ(1:1)中Ni含量较高,为187.67 mg·kg-1外,各处理中重金属Cd、Pb、Cu、Zn、Cr含量都显著低于国家农用标准(GB 4284-84、GB 8173-87).     

皂角苷和柠檬酸联合对污泥中Cu、Pb和Zn的去除及其稳定性特征

以武汉某污水处理厂的污泥为研究对象(S1和S2),通过皂角苷和柠檬酸联合振荡淋洗试验,研究不同体积比(20∶1~1∶20)、固液比(1∶20~1∶80)、淋洗时间(0~2 880 min)、淋洗次数(1~4)对污泥中重金属Cu、Pb和Zn去除的影响.分析淋洗前后各形态重金属的去除特点,并通过计算稳定性指数(I_R值)和移动性指数(MF值)探究重金属稳定性和移动性的变化.结果表明,在体积比(皂角苷∶柠檬酸)为5∶1,固液比为1∶60,淋洗时间1 440 min时,污泥中Cu、Pb和Zn的最高去除率分别可达43.16%(S1)、32.45%(S2)和38.69%(S1).增加淋洗次数对Cu和Pb的去除率有较大幅度提高,而对Zn的影响较小,尤其在2~3次淋洗后差异显著.4次淋洗后Cu、Pb和Zn的最高去除率分别为78.89%(S1)、77.08%(S2)和49.39%(S1).单次淋洗后,除酸溶态和可还原态外,污泥中其余形态的去除率均较低.增加淋洗次数,重金属的各形态去除率逐渐升高,尤其是Pb中的残渣态去除率增长明显.淋洗改变了重金属的稳定性和移动性,4次淋洗后Cu、Pb和Zn的IR值最大增长率分别为43.63%(S1)、39.44%(S2)和32.00%(S1),MF值减少30.19%~79.45%.     

广州城市污泥中重金属的存在特征及其农用生态风险评价

分析了广州7种城市污泥中Zn、Cu、Pb、Cr、Mn、Ni的含量,研究了其中5种污泥中重金属的形态特征,并利用地累积指数（Igeo）和潜在生态危害指数法（RI）对污泥农用过程中重金属的潜在生态风险进行了综合性评价. 结果表明,广州不同来源城市污泥中Cu、Zn、Mn、Ni含量较高,变化幅度较大,而Pb、Cr含量较低. 除一种污泥中Cu超标外,其他重金属基本符合国家农用控制标准（GB18918-2002）,但所有污泥中重金属含量都超过珠江三角洲耕地土壤均值.不同重金属在不同污泥中的形态分布差异较大. 其中,含工业污水污泥中Cu、Cr还原态占很大的比例,Pb、Fe主要以还原态和残渣态存在;生活污水污泥中重金属主要以可氧化态和残渣态存在,酸可交换态中Mn的比例较高,易还原态中Zn的比例较高;5种污泥中Cu、Zn、Mn潜在迁移性最强.Igeo和RI评价结果表明,污泥中Cu、Zn、Mn是潜在的强生态风险元素,污泥在农用过程中具有一定生态风险性. Igeo和RI用于污泥农用过程中重金属的生态风险评价是可行的,与其它评价方法相比较, RI能更好地反映污泥中重金属对生态环境的综合影响.     

钙基膨润土辅助对堆肥及土壤Cu、Zn形态转化和白菜吸收的影响

通过好氧堆肥和盆栽试验,探究不同比例（0%、2.5%、5%、7.5%和10%）钙基膨润土（CB）辅助猪粪堆肥过程及盆栽土壤中Cu、Zn形态的变化,并分析CB对白菜生物量及吸收Cu、Zn的影响.结果表明,在所有处理的堆肥过程中,可交换态Cu、Zn的分布比例逐渐下降,而可氧化态和残渣态逐渐升高,与0% CB相比,2.5%~10% CB可使堆肥结束时生物可利用态（可交换态和可还原态）Cu、Zn的分布比例分别降低19.84%~48.90%和4.94%~16.39%,并以10% CB的效果最为显著.进而开展的盆栽试验显示,施用堆肥后,土壤有机质和EC显著升高,而pH有所下降;CB辅助堆肥能够促使土壤EC的降低及pH的升高,稳定土壤有机质.与纯土处理相比,施用堆肥可显著提升白菜的生物量,且10% CB处理中的生物量最大（6.51 g·盆^-1±0.34 g·盆^-1）.施用CB辅助堆肥后,种后土壤中生物可利用态Cu含量增加;但各处理中可交换态Zn含量分别降低38.91%、43.69%、46.02%、45.12%和54.65%.白菜在施用堆肥后Cu、Zn的吸收量显著降低,并且随着CB辅助比例的增加Zn的吸收量随之减少,而Cu的吸收量呈增加趋势.本研究表明,钙基膨润土能够降低堆肥过程中Cu、Zn活性,在堆肥施入土壤后仍对Zn有持续的固定作用,同时CB辅助堆肥可以提高白菜的生物量,减少重金属Zn在白菜中的累积,并以10% CB的效果最为显著.     

东北地区城市污水处理厂污泥中重金属的形态分布及其潜在生态风险评价

分析了东北地区7个城市污水处理厂脱水污泥中Cu、Zn、Cr、Ni、Mn的含量,利用修正的BCR法研究了污泥中重金属的形态分布特征,并使用地累积指数(Igeo)法和内梅罗指数法(PI)评估了污泥在土地利用过程中重金属的潜在生态风险.结果表明,污水厂污泥中Zn含量超过了国家标准(GB4284—1984)限值,且污泥中Cu、Zn和Mn的含量远远超过东北耕地黑土中的背景含量.污泥中Cu和Cr的有机物结合态(即可氧化态)所占比例较大,可迁移形态含量最高的重金属是Zn,Ni广泛分布于可交换态、酸溶态、可还原态、可氧化态和残渣态中,Mn的残渣态在5种形态中所占比例最高.5种金属中迁移性最强的是Zn,其次为Mn,Cr的迁移性最差.内梅罗单项污染指数法和地累积指数法的评价结果表明,Cu、Zn和Mn是污泥土地利用过程中潜在的污染元素.内梅罗综合指数法的评价结果显示,种脱水污泥均对耕地黑土环境存在严重的潜7在生态风险.     

我国城市污泥中重金属的赋存形态与生态风险评价

为全面了解中国城市污水处理厂脱水污泥中重金属（HMs）的形态特征和污染状况,本研究以我国40座城市污水处理厂的剩余污泥为研究对象,对污泥中重金属As、Cd、Cr、Cu、Ni、Pb和Zn的总量以及赋存形态进行了测定.采用毒液浸出法（TCLP）、风险评价编码法（RAC）和潜在生态风险指数法评价了其生态风险.结果表明,40个样品中重金属含量的中位值由大到小依次为：Zn > Cu > Cr > Pb > Ni > As > Cd,各元素整体达标率>90%.As的各形态分布较为平均;Cd和Zn以可还原态为主;Cr主要以残渣态的形式存在,其次为可氧化态和可还原态;Cu主要以可氧化态的形式存在;Ni主要以可交换态的形式存在;Pb主要以可还原态和残渣态的形式存在,可交换态的含量最低.TCLP提取态重金属的比例大小顺序为：Ni > As > Zn > Cd > Cu > Cr,所有样品中Pb的TCLP提取态含量均低于检出限;RAC法评价结果显示,7种重金属环境风险大小依次为：Ni > As > Zn > Cd > Cu > Cr > Pb,Ni的生态风险等级为高等,Zn、As和Cd的生态风险等级为中等,Cr和Cu的生态风险等级为低等,Pb无生态风险;潜在生态风险评价结果表明,城市污泥中Cd和Cu的潜在生态风险最高,是我国城市污泥中主要的重金属污染物,但是如果按照国家标准规定的方法进行农用,造成土壤污染的风险总体处于较低水平.     

中国城市污泥的重金属含量及其变化趋势

对相关研究结果的系统统计表明，Zn是我国城市污泥中平均含量最高的重金属元素，其次是Cu，再次是Cr，而毒性较大的元素Hg、Cd、As含量往往较低，通常在几个到十几个mg/kg范围内；70％统计样本的As含量在20ms／kg以内，而Cd、Cr、Ca、Hg、Ni、Pb、Zn含量则分别在2．8、250、417、5、75、130、1701ms／kg以内．我国城市污泥中的重金属含量普遍低于英美等发达国家，而且其中的重金属含量呈现逐渐降低的趋势．按照1984年颁布的《农用污泥污染物控制标准》(GB4284-84)，Zn是我国城市污泥中超标问题最突出的重金属，其超标率为55％；但按照2002年新修订的《城镇污水处理厂污染物排放标准(报批稿)》，Zn的超标率仅为9％．一方面，我国的土壤和儿童普遍缺Zn，另一方面，我国现行的农用污泥污染物控制标准对城市污泥中的Zn控制过于严格，而且也不尽合理，急需对其进一步完善，以合理解决城市污泥的处理处置途径，推动城市污泥的资源化和无害化利用．     

皂角苷和柠檬酸联合对市政污泥中重金属的去除与风险评价

污泥的重金属污染严重制约其资源化利用,为探讨皂角苷和柠檬酸联合淋洗去除污泥中重金属的效果,为污泥的资源化利用提供理论依据,以武汉市4个市政污泥样品(S₁、S₂、S₃、S₄)为研究对象,选取1%的皂角苷和0.1 mol/L的柠檬酸联合淋洗1~4次,对淋洗前后污泥中重金属Cu、Ni、Pb、Zn、Cd和Cr的含量和形态进行了分析,并运用M_F指数法和潜在生态风险指数法对淋洗后污泥中重金属的迁移性和环境效应进行了评价。结果表明:经过1次淋洗后,污泥中Zn的去除率最高,为71.04%(S₁),而Ni的去除率较低,为20%左右(S₂),污泥中Cr、Cu、Pb和Cd的最大去除率在23.16%~43.00%之间;经过4次淋洗后,污泥中Zn、Pb、Cr、Cu、Cd和Ni的去除率最高分别为84.79%、81.73%、80.77%、78.89%、56.71%和55.51%;经过淋洗后污泥中各重金属酸溶态所占的比例降至5.41%以下,污泥中Cu以残渣态和可氧化态为主,其他重金属以残渣态为主;皂角苷与柠檬酸联合淋洗后,污泥中重金属的M_F(移动性指数)和E_i(潜在生态风险指数)值下降,说明污泥中重金属的移动性、生物有效性和潜在生态风险减弱,其中污泥中Ni、Pb、Zn的潜在生态风险均由中降为低,污泥中Cu、Cr和Cd的潜在生态风险也有所降低;1.5 g/L的熟石灰对污泥淋洗废液中Cu、Ni的回收率在25%左右,对Pb、Zn、Cd、Cr的回收率在58%~80%之间。皂角苷和柠檬酸联合淋洗可以较好地去除供试污泥中的重金属,降低重金属的移动性和潜在生态风险。     

Solubility of ion and trace metals from stabilized sewage sludge by fly ash and alkaline mine tailing

Stabilized sewage sludge （SS） by fly ash （FA） and alkaline mine tailing as artificial soil, to be applied on the ecological rehabilitation at mining junkyards, offers a potentially viable utilization of the industrial by-product, as well as solves the shortage of soil resource in the mine area. An incubation experiment with different ratios of SS and FA was conducted to evaluate the solubility of ions and trace elements from stabilized sewage sludge. Results showed that fly ash offset a decrease in pH value of sewage sludge. The pH of （C） treatment （FA：SS = 1：1） was stable and tended to neutrality. The SO4^2- and Cl^- concentrations of the solution in the mixture were significantly decreased in the stabilized sewage sludge by alkaline fly ash and mine tailing, compared to the single SS treatment. Stabilized sewage sludge by FA weakened the nitrification of total nitrogen from SS when the proportion of FA in the mixture was more than 50%. The Cr, Ni, and Cu concentrations in the solution were gradually decreased and achieved a stable level after 22 days, for all treatments over the duration of the incubation. Moreover stabilized sewage sludge by fly ash and/or mine tailing notably decreased the trace metal solubility. The final Cr, Cu, and Ni concentrations in the solution for all mixtures of treatments were lower than 2.5, 15, and 50 μg/L, respectively.     

污泥对樟子松生物量及其重金属积累和土壤重金属有效性的影响

采用盆栽试验研究了不同剂量污泥(体积分数,即污泥体积占污泥和沙土总体积的百分比,分别为:0、20%、33.3%、50%和100%)施用于风沙土条件下,污泥剂量对樟子松幼苗生物量及其对重金属的累积和土壤中重金属有效性的影响.结果表明,在养分含量低的风沙土中,施用污泥能够显著提高樟子松幼苗生物量,最适剂量为50%;污泥剂量的增加可促进樟子松植株对重金属的吸收和累积,在最适剂量(50%)条件下,樟子松植株中Cu、Cd、Pb、Zn的累积量分别是对照(不施污泥)的18.0、8.9、17.1、11.5倍;樟子松植株重金属吸收速率顺序为:ZnCuPbCd,而迁移系数顺序为:ZnCdCuPb;土壤中有效态重金属含量随污泥剂量的增加而增加,而植株收获后土壤中有效态重金属下降幅度均小于对照.     

Effect of substrate concentration on the bioleaching of heavy metals from sewage sludge

IntroductionTheproductionofexcesssewagesludgeisincreasingrapidlywiththewidespreadofwastewatertreatment,whichcausesseriousproblemtothedisposalofsewagesludge .Landapplicationofsewagesludgeisthemostcost effectiveandfeasibleutilizationapproachatpresent.Howeve…     

广州城市污泥中重金属形态特征及其生态风险评价

分析了广州市4个不同来源的城市污水处理污泥中重金属含量,考察了污泥样品中重金属形态分布和生物可利用性,并分别利用风险评价指数(RAC)和固废重金属毒性浸出方法评价了污泥中重金属生态危害风险和浸出毒性风险.结果表明,污泥样品中Cu、Cr、Pb和Zn含量较高,不同来源污水处理污泥中重金属含量差别较大.污泥样品中重金属绝大部分以非稳定态存在,酸性污泥中可迁移的酸溶态重金属比例较高.由单一萃取结果,1 mol·L-1NaOAc溶液(pH 5.0)和0.02 mol·L-1EDTA+0.5 mol·L-1NH4OAc溶液(pH 4.6)分别对酸性和碱性污泥中生物可利用态重金属具有较好的萃取能力.污泥酸性越强,其中生物可利用态重金属比例越大.污泥中重金属的迁移能力使其处于高生态危害风险程度;重金属的生物可利用性使酸性污泥大多处于极高危害风险程度,而使碱性污泥大多处于中等危害风险水平.除城市污水处理污泥外,污泥样品中重金属具有高的浸出毒性风险,萃取重金属生物可利用态后,污泥仍具有高浸出毒性风险,但由于浸出毒性风险降低使部分污泥可进行填埋处置.     

Characteristics of sewage sludge and distribution of heavy metal in plants with amendment of sewage sludge

In order to better understand land application of sewage sludge, the characterization of heavy metals and organic pollutants were investigated in three different sewage sludges in Shanghai City, China. It was found that the total concentrations of Cd in all of sewage sludge and total concentrations of Zn in Jinshan sewage sludge, as well as those ofZn, Cu, and Ni in Taopu sludge are higher than Chinese regulation limit of pollutants for sludge to be used in agriculture. Leachability of rig in all of studied samples and that of Cd in Taopu sewage sludge exceed the limit values of waste solid extraction standard in China legislation. Based on the characteristics for three kinds of sewage sludge, a pot experiment was conducted to investigate the effect of soil amended with Quyang sewage sludge on the accumulation of heavy metalo.by Begonia semperfloreas-hybr; Ophiopogon japonicas （L.F.） Ker-Gaw; Loropetalum chindense-var, rubrum; Dendranthema morifolium; Viola tricolor; A ntirrhinum majas; Buxas radicans Sieb; Viburnum macrocephalum; Osmanthas fragrans Lour; Cinnamomum camphora siebold and Ligustrum lucidum ait. Results showed that 8 species of plant survived in the amended soil, and moreover they flourished as well as those cultivated in the control soil. The heavy metal concentration in plants varied with species, As, Pb, Cd and Cr concentration being the highest in the four herbaceous species studied, particularly in the roots of D. morifolium. These plants, however, did not show accumulator of As, Pb, Cd and Cr. The highest concentration of Ni and Hg was found in the roots ofD. morifolium, followed by the leaves ofB. semperflorens-hybr. Levels of Zn and Cu were much higher in D. morifolium than in the other plant species. D. morifolium accumulated Ni, Hg, Cu and Zn, which may contribute to the decrease of heavy metal contents in the amended soil. Treatment with sewage sludge did not significantly affect the uptake of heavy metals by the L. chindense-var, rubrum, however, it significantly affected the uptake of heavy metals by D. morifolium.     

Investigation on Fe, Mn, Zn, Cu, Pb and Cd fractions in the natural surface coating samples and surficial sediments in the Songhua River, China

Natural surface coating samples （NSCSs） from the surface of shingles and surficial sediments （SSs） in the Songhua River, China were employed to investigate the relationship between NSCSs and SSs in fractions of heavy metals （Fe, Mn, Zn, Cu, Pb, and Cd） using the modified sequential extraction procedure （MSEP）. The results show that the differences between NSCSs and SSs in Fe fi＇actions were insignificant and Fe was dominantly present as residual phase （76.22% for NSCSs and 80.88% for SSs） and Fe-oxides phase （20.33% for NSCSs and 16.15% for SSs）. Significant variation of Mn distribution patterns between NSCSs and SSs was observed with Mn in NSCSs mainly present in Mn-oxides phase （48.27%） and that in SSs present as residual phase （45.44%）. Zn, Cu, Pb and Cd were found dominantly in residual fractions （〉48%）, and next in solid oxides/hydroxides for Zn, Pb and Cd and in easily oxidizable solids/compounds form for Cu, respectively. The heavy metal distribution patterns implied that Fe/Mn oxides both in NSCSs and SSs were more important sinks for binding and adsorption of Zn, Pb and Cd than organic matter （OM）, and inversely, higher affinity of Cu to OM than Fe/Mn oxides in NSCSs and SSs was obtained. Meanwhile, it was found that the distributions of heavy metals in NSCSs and SSs were similar to each other and the pseudo-total concentrations of Zn, Cu, Pb and Cd in NSCSs were greater than those in SSs, highlighting the more importance for NSCSs than SSs in controlling behaviours of heavy metals in aquatic environments.     

广州市污水污泥中的重金属及其农用探讨

分析了广州市6种污水污泥中重金属(Zn,Cu,Pb,Cr,Mn和Ni)质量分数及其存在形态,并对污泥农业利用过程中施用的最大量进行了估算.结果表明:广州不同来源污水污泥中.(Cu),w(Zn),w(Mn)和,(Ni)较高,变幅较大,而w( Ph )和w( Cr)低.除一种污泥中w(Cu)超标外,其他重金属基本符合国家农用控制标准(G1318918-2002),但所有污泥中重金属质量分数都超过广州市农田土壤平均值.不同重金属以及同一重金属在不同污泥中的形态分布也不同,其中Zn,Mn和Ni的潜在迁移性强,Cu和Cr中的还原态占有很大的比例,污泥中Pb主要以还原态和残渣态存在.根据广州市主要旱地赤红色土壤静态环境容量和动态环境容量计算表明,污泥农用过程中Cu和Zn是主要监控污染元素,不同来源污泥的最大施用量有明显差异.为保证土壤环境的安全,建议将Cu和Zn作为控制城市污水污泥农用过程中最高施用量的计算参考指标.     

Mobilities and teachabilities of heavy metals in sludge with humus soil

Chemical forms of Zn, Ni, Cu, and Pb in municipal sewage sludge were investigated by adding humus soil to sludge and by performing sequential extraction procedures. In the final sludge mixtures, Zn and Ni were mainly found in Fe/Mn oxide-bound (F3) and organic matter/sulfide-bound (F4) forms. For Zn, exchangeable (F1), carbonate-bound (F2), and F3 forms were transformed to F4 and residual forms (F5). For Ni, Fl and F2 forms were transformed to Fl, F2, and F3 forms. Both Cu and Pb were strongly associated with the stable forms F4 and F5. For Cu, F2 and F3 forms were major contributors, while for Pb, F3 and F4 forms were major contributors to F5. Humus soil dosage and pH conditions in the sludge were strongly correlated with the forms of heavy metals. Five forms were used to evaluate metal mobilities in the initial and final sludge mixtures. The mobilities of the four heavy metals studied decreased after 28 days. The metal mobilities in the final sludge mixtures were ranked in the following order: Ni > Zn > Cu = Pb. Leaching tests showed that the mobilities of Zn and Ni in lower pH conditions (pH 4) were higher than those in higher pH conditions (pH 8).     

Zn、Cd单一及复合污染对黑麦草根分泌物及根际Zn、Cd形态的影响

采用根袋土培试验,研究了锌、镉单一及复合污染对重金属富集植物黑麦草生长、锌镉积累、根分泌物及根际Zn、Cd形态的影响.结果表明,锌镉共存下(8 mmol/kg Zn+2 mmol/kg Cd),黑麦草对锌、镉的吸收为协同效应;仅镉污染时(2 mmol/kg Cd),镉对植株吸收锌为抑制效应.黑麦草吸收的锌、镉主要集中在地上部,以锌、镉复合污染时植株地上部对锌、镉的富集量最大,分别达到3 108.72、73.97 mg/kg,具有作为土壤重金属锌、镉污染植物修复材料的潜力.根际的松结合态锌、镉（交换态、碳酸盐结合态和铁锰结合态）含量大于其非根际的松结合态锌、镉含量.Cd污染和Zn、Cd复合污染的根际和非根际土壤镉形态均以交换态>碳酸盐结合态>铁锰结合态>残渣态>有机结合态.Zn污染及Zn、Cd复合污染根际和非根际土壤各锌形态以铁锰结合态>碳酸盐结合态>残渣态>有机结合态>交换态,而Cd污染的根际和非根际的锌形态则以残渣态>铁锰结合态>有机结合态>碳酸盐结合态>交换态.Zn、Cd污染促进了黑麦草根系氨基酸的分泌,降低了根际土壤的pH值,以Zn、Cd复合污染根际土壤氨基酸总量最大,分别为对照、Zn和Cd污染的1.95、1.54和1.40倍,根际土壤的pH值最低(5.18).根际氨基酸含量在重金属胁迫下明显增加,可能与黑麦草适应重金属胁迫有关.根际pH值高于非根际是根际Zn、Cd有效性大于非根际的重要原因.     

Mobilities and leachabilities of heavy metals in sludge with humus soil

Chemical forms of Zn, Ni, Cu, and Pb in municipal sewage sludge were investigated by adding humus soil to sludge and by performing sequential extraction procedures. In the final sludge mixtures, Zn and Ni were mainly found in Fe/Mn oxide-bound (F3) and organic matter/sulfide-bound (F4) forms. For Zn, exchangeable (F1), carbonate-bound (F2), and F3 forms were transformed to F4 and residual forms (F5). For Ni, F1 and F2 forms were transformed to F1, F2, and F3 forms. Both Cu and Pb were strongly associated with the stable forms F4 and F5. For Cu, F2 and F3 forms were major contributors, while for Pb, F3 and F4 forms were major contributors to F5. Humus soil dosage and pH conditions in the sludge were strongly correlated with the forms of heavy metals. Five forms were used to evaluate metal mobilities in the initial and final sludge mixtures. The mobilities of the four heavy metals studied decreased after 28 days. The metal mobilities in the final sludge mixtures were ranked in the following order: Ni > Zn > Cu = Pb. Leaching tests showed that the mobilities of Zn and Ni in lower pH conditions (pH 4) were higher than those in higher pH conditions (pH 8).     

Trace element speciation in selected smelter-contaminated soils in Anaconda and Deer Lodge Valley, Montana, USA

Long-term copper smelting in the Anaconda and Deer Lodge Valley area of Montana has resulted in an extensive area of trace element contamination. Aerial extent of contamination is generally established, but total analysis of soils does not correlate to relative degree of impact on vegetation growth. Three pedons (Beaverell, Cetrack and Judco) were analyzed by routine soil characterization methods, aqua regia microwave digestion, sequential chemical extraction, and X-ray diffraction analysis with the objective of providing a better understanding of chemical forms and potential reactivity of selected trace elements (Cd, Co, Cr, Cu, Hg, Mn, Ni, P, Pb). Surface horizons of soils are more acidic than subsoils, with pH for all horizons ranging from 4.0 to 8.7. Beaverell is the most contaminated in the upper 20 cm with the sum of total extractable (SUM_TE) trace elements by microwave digestion ranging from 1836 to 3605 mg kg⁻¹, largest H₂O-soluble (WS) and exchangeable (EX) fractions (e.g. 1.6 and 9.3%, respectively), and smallest residual (RES) fraction (e.g. 14.3%). Cetrack has greater SUM_TE elements than Judco, though a lower WS+EX fraction due to the effects of alkaline pH, carbonates and high P. Oxide (OX), organic matter/sulfide (OM/S), and RES fractions predominate over WS, EX, and specially-sorbed/carbonate-bound fractions (SS/CAR) for all horizons. Copper, Zn, Pb and Cd are elevated in surface over subsurface horizons in these latter fractions, indicating these elements were anthropogenic additions. X-ray data indicate that Pb, Cu, Cr and Cd partially exists as both OX and sulfide mineral forms.